The causes of the more than 80,000 new cases of leukemia and lymphoma each year in the US are largely unknown. "Clusters" of leukemias have been found near Superfund sites and other hazardous facilities, raising public concern over the role environmental chemicals. New methods are needed to determine what risk factors play a role in leukemia development and to predict which chemicals might cause leukemia. In the past few years, many of the important genetic changes associated with leukemia have been identified. Further, it has been realized that these changes must occur in early progenitor or stem cells residing in the bone marrow. Hence, chemicals with the potential to cause leukemia should be tested for their ability to produce genetic changes associated with leukemia in cultured stem cells. Fortunately, methods for the isolation and culture of stem cells from peripheral blood have recently been developed. In addition, methods which can detect important genetic changes associated with leukemia have also been developed. These methods are based on fluorescence in situ hybridization (FISH) and reverse transcriptase - PCR (rt-PCR). We propose to use these methods and the micronucleus assay to determine if selected chemicals, including those found at Superfund sites, can produce genetic damage of relevance to leukemia in cultured lymphocytes and progenitor (stem) cells in culture. Further, we plan to use FISH and rt-PCR to characterize the genetic changes occurring in 200 new cases of childhood leukemia with Project 6. This will allow for subclassification of the leukemias so that new associations with chemical exposures can be observed. In particular. In particular, the timing and prevalence of various chromosomal translocations will be determined. Recent evidence suggests that a large number of these translocations occur as a result of aberrant V (D)J recombinase activity. We therefore propose to determine if aberrant V(D)J recombinase activity can be induced by selected chemicals. We will also determine if the cases of childhood leukemia have a higher level of aberrant V(D)J recombinase-mediated events in their peripheral blood. This will provide further insight into the role of aberrant V(D)J recombinase activity in producing leukemia. We also propose to test the hypothesis that B-lymphocytes may be better surrogates than T-cells in biomarker epidemiology studies of human populations. We will test the ability of various chemicals to produce genetic damage in B- and T-lymphocytes and directly compare the data produced. Further, we will determine the role of genetic polymorphisms in glutathione transferase isoenzymes in human susceptibility to chemically induced genetic damage (in collaboration with Project 4). Thus, new assays will be developed to better predict which chemicals are likely to cause human leukemia. In addition, together with investigators from Projects 4 and 6, we will determine what factors most likely contribute the development of leukemia, a disease commonly clustering near Superfund sites.